In the operation of screw machines of known design, the bar stock is fed into the machine in long lengths and has had a very considerable tendency to vibrate transverse to its length. Usually, the rotating bar stock is passed through an elongated guide tube held stationary at the inlet side of the screw machine. The rotating bar stock has a loose fit inside the non-rotating guide tube and it is free to vibrate transversely, striking the tube and thereby causing appreciable noise and often damaging the bar stock itself, particularly if it is of hexagonal or other polygonal, sharp cornered cross-section. Excessive noise in a machine shop is an occupational harzard which can be damaging to the safety, health and well-being of workers there and is contrary to federal policy, as expressed in the Occupational Safety and Health Act.
My U.S. Pat. No. 4,566,358 discloses a bar stock guide which does away with the usual continuous guide tube and instead provides a rotatably mounted fitting which has a horizontal opening for loosely passing the bar stock and guide rollers in the fitting at circumferentially spaced locations around the bar stock. The guide rollers are on roller supports which are radially slidable in the fitting and have rack teeth on their opposite sides. Weights are slidable radially in the fitting between the successive roller supports, and these weights have rack teeth in their opposite sides. Pinion gears are mounted in the fitting to engage the rack teeth on the roller supports and the weights so that centrifugal force on each weight produces an inward force on the neighboring roller support. Springs bias the weights radially outward.
My U.S. Pat. Nos. 4,000,797 and 4,030,585 disclose bar stock guides generally similar to those disclosed in U.S. Pat. No. 4,566,358 but differing from it in that the guide rollers are resiliently mounted in various ways.